Is altruism something that's unique to primates? Neuroscientists Peggy Mason and Inbal Ben-Ami Bartal decided to find out, using rats. What they discovered is these rodents will help each other escape from locked cages. They will even share their favorite food with rats.

Mason and Bartal placed pairs of rats in Plexiglass pens. One rat was trapped in a cage in the middle of the pen, whereas the other rat was free to run around. Most free rats circled their imprisoned peer, gnawing at the cage and sticking their paws, noses and whiskers through any openings. After a week of trial and error, 23 of the 30 rats in the experiment learned to open the cage and free their peers by head-butting the cage door or leaning their full weight against the door until it tipped over. (The door could only be opened from the outside.) At first the rats were startled by the noise of the toppling door. Eventually, however, they stopped showing surprise, which suggests that they fully intended to push the door aside. Further, the rodents showed no interest in opening empty cages or in those containing toy rats, indicating that a break out was their genuine goal.

In this first set of experiments, most rats seemed quite willing to help their peers, but Mason wanted to give them a tougher test. She placed rats in a Plexiglass pen with two cages: in one was another rat, in the other was a pile of five milk chocolate chips-a favorite snack of these particular rodents. The unrestricted rats could easily have eaten the chocolate themselves before freeing their peers or been so distracted by the sweets that they would neglect their imprisoned friends. Instead, most of the rats opened both cages and shared in the chocolate chip feast.

Other studies have shown that rats will spend more time with cagemates who are ill or distressed. This behavior is an echo of what humans do when they comfort an ill friend. These studies, and several others, suggest that altruism goes beyond the hominid world. And Mrs. Frisby and the Rats of NIMH may be closer than you think.